Cold working tool for openings in metal pieces

Abstract

A segmented mandrel for cold working having two forward segments and two rear segments positioned between the two forward segments, when fitted together have an approximately circular outline. The two forward segments and the two rear segments are movable separately and together.

What is claimed is: 
     
       1. A cold working tool for openings in metal pieces, comprising:
 a segmented mandrel having four segments including two forward segments opposing each other and two rear segments opposing each other alternatingly positioned between the two forward segments, 
 wherein the two forward segments and the two rear segments when fitted together have an approximately circular cross-section, 
 wherein each segment of the two forward segments and each segment of the two rear segments has a substantially quarter-cylinder form with a curved outer surface, a flat inner surface opposite the curved outer surface and connecting surfaces between the outer and inner surfaces, and 
 wherein the connecting surfaces of the two forward opposing segments are slightly relieved starting from a distance from distal ends of the two forward segments a distance toward proximal ends thereof to permit the two rear segments to inwardly press adjacent the two forward segments and permit the two rear segments and the forward two segments to pass through an opening in a metal workpiece to a position where distal ends of all the segments extend beyond a distal end of the opening and then, when the two rear segments are moved farther through the opening to match the extent of the two forward segments, to move radially outward so that the circumference of the segmented mandrel is larger than the opening in the metal workpiece, while the proximal end of the segmented mandrel remains outside a proximal end of the opening for pulling of the segmented mandrel so that the opening in the metal piece is cold worked as the mandrel is pulled back through the opening. 
 
     
     
       2. The cold working tool of  claim 1 , wherein the outer surfaces of the two forward segments and the two rear segments are substantially identical. 
     
     
       3. The cold working tool of  claim 1 , wherein the inner surfaces of the two forward segments are slightly smaller in width than the inner surfaces of the two rear segments. 
     
     
       4. The cold working tool of  claim 1 , wherein the connecting surfaces of the two forward segments are relieved approximately 0.003-0.050 inches extending toward the proximal ends of the two forward segments starting from approximately 0.8 inches from the distal ends of the two forward segments. 
     
     
       5. The cold working tool of  claim 1 , wherein the two rear segments are axially moveable relative to the two forward segments and wherein the two forward segments and the two rear segments also are axially moveable together.